Background: Basal cell carcinoma (BCC) is the most common type of skin cancer in humans. Photodynamic therapy (PDT) is a non-invasive therapeutic modality that may be considered as a valuable treatment option for BCC. This study was designed with the aim of evaluating the efficacy of PDT in treatment of BCC and factors that may affect the response rate. Materials and Methods: This clinical trial was conducted on 12 patients (28 BCC lesions) who were treated with aminulevulinic acid (ALA)-PDT, monthly, up to 6 sessions and the clinical response, cosmetic results, and possible side effects were evaluated. Results: The study was performed on 28 BCC lesions from 12 patients. Complete response was achieved in 9 (32.1%) lesions. Complete response rate was higher in younger patients ( P < 0.01) and those with smaller lesions ( P < 0.001). Superficial type also had significant higher response rate ( P < 0.05). Patients with history of radiotherapy for the treatment of tinea capitis in childhood showed less response ( P < 0.05). Cosmetic results were excellent or good in 77.5% cases. After 6 months of follow-up, none of the resolved lesions recurred. Conclusion: PDT would be a good therapeutic option in treatment of BCC with acceptable efficacy and low side effects. Younger patients, superficial BCCs, and smaller lesions show better response to ALA-PDT. History of radiotherapy may be associated with a lower response rate.